Methods for manufacturing an isotopic filtration module and methods for filtering water according to its isotopic forms. In some implementations, graphene oxide flakes may be dispersed in an aqueous medium to form a graphene oxide solution. The graphene oxide solution may be applied to a substrate to form a laminated graphene oxide membrane comprising a plurality of graphene oxide sheets coupled together in a layered, interlocking structure. The laminated graphene oxide membrane may be positioned in a filtration housing configured to be coupled with a wastewater stream of a nuclear power plant in order to filter the wastewater stream according to its isotopic forms.